(1) Technical Field
The subject invention is related to light weight panels that form the walls of a cargo trailer and more particularly to extruded hollow panels that are connected together to form an inside wall surface in a continuous vertical plane and an outside surface in a continuous vertical plane.
(2) Description of the Prior Art
Trailers and cargo bodies mounted on trucks have employed walls with a variety of different constructions. The construction used has been dependent on the material to be transported, weight restraints, material available for wall construction, cost, available fabrication equipment, customer demand and other factors. Little or no consideration has been given to repairability. Purchasers do not expect to damage the walls of their trailers and truck bodies so minimal consideration has been given to repairability.
The walls of many trailers have internal vertical frame members and an outside sheet metal cover connected to the frame members. Where weight is not a paramount consideration the inside can be lined with plywood. Plywood panels can be removed and replaced as required. When weight is a consideration, a sheet metal cover also lines the inside of the frame. To reduce problems caused by water leaks some manufacturers have installed metal sheets that extend from the front to the rear on both the inside and the outside. If one of the outside metal sheets is damaged, it may be necessary to remove all the rivets from an inside sheet to obtain access to the rivets for the outside sheet, replace the outside sheet and then reattach the inside sheet. Removal and replacement of rivets is a time consuming and costly process. Making such a repair may exceed ten percent of a cost of a new trailer and take several days to complete. The rivets employed in wall construction can damage cargo packages and cargo at times. With thin metal panels, the heads of rivets cannot be countersunk.
There are trailers and truck mounted cargo containers that have frame or stake members that are exposed on the outside and have metal panels secured to the inside surfaces. These trailers can be repaired and are relatively light weight. However, the exposed stake members create substantial wind resistance, reduce fuel mileage and increase operating cost. A moisture leak around any of the rivets connecting the inside metal panels to the stakes may lead to water damaged cargo.
The walls of trailers have also been made from one piece fiberglass reinforced plywood (FRP) panels. These panels have a plywood core encased in a tough reinforced resin cover. Many of the drawbacks of the above described trailer wall constructions are eliminated by the FRP panels. They have sufficient strength to eliminate stakes and other reinforcing members. The surfaces of the panels are smooth on the inside and outside. Unfortunately FRP panels also have major disadvantages. They are heavy, difficult to ship and expensive. Special handling equipment is required to assembly a trailer with wall panels that can be over 8 feet high, 60 feet long, heavy, and have slick surfaces. If an FRP panel is damaged and has to be replaced it will most likely have to be returned to the factory where it was built for repair or at least to a facility that has equipment similar to the equipment found in the factory.